This has been a problem for every Internet service everywhere ever. That hasn't stopped email from being useful, forums from being useful, traditional wikis (weird to say "traditional wikis", now that there's a new kind of wiki) from being useful, websites from being useful, etc.
The spam problem always has to be solved. That said, very active wikis have shown themselves to be more resistant to spammers than most online services. Because anyone can remove the spam, there's a pretty high cost to keeping the spam flowing, particularly if there are sufficient impediments to automation in place.
Of course every non-moderated service has spam, that was kinda the point of my post... Maybe the part you missed was that they introduced a new way of spamming via forking pages... I don't think I ever made any allusions to something not happening because of it. Thanks for the pep talk though, I'll keep it in mind as I do my nightly task of helping clean up spam on the sites where I moderate.
Spamming via forking seems, to me, to be very similar to trackback spam on blogs. But, yes, it will probably require a bit of novelty in terms of how one fights it.
The spam problem always has to be solved. That said, very active wikis have shown themselves to be more resistant to spammers than most online services. Because anyone can remove the spam, there's a pretty high cost to keeping the spam flowing, particularly if there are sufficient impediments to automation in place.